Field of the Invention
This invention relates to improvements in agent dispensers in the form of fluid imbibing pumps and, more particularly, to an implantable agent dispenser having an improved closure.
This invention relates to fluid imbibing osmotic pumps of the type described in U.S. Pat. Nos. 3,760,984, 3,977,790, 3,995,631, 4,034,756, 4,474,575 and 4,539,004, all of which are incorporated herein by reference. An agent dispenser which is osmotically driven is disclosed in each of these patents. Such an agent dispenser is capable of having a size which renders it suitable for use as a therapeutic device for administering agents, particularly drugs to animals and humans when the agent dispenser is exposed to body fluids on the skin, under the skin or in a body cavity such as the gastrointestinal tract or the vagina, for example.
An agent dispenser of the type described includes the following components: an outer membrane, at least a portion of which is permeable to fluids, such as water; an inner agent receiving means, such as a flexible bag that holds a flowable agent to be dispensed; and an intermediate fluid imbibing means such as a layer of an osmotically effective solute composition, such as an inorganic salt. A discharge port is provided for the bag to allow the agent contained therein to be directed out of the bag and to a point of use.
Actuation of the agent dispenser is achieved after an agent has been directed into the bag and the agent dispenser has been in an environment, such as on the skin, below skin level, or in a body cavity. Body liquids are imbibed from the environment by the solute through the membrane and into the space between the inner bag and the membrane. The imbibed water squeezes and collapses the bag, thereby causing the agent in the bag to be forced out of the bag through and out of the discharge port.
There are numerous problems associated with state of the art dispensers such as the expense and difficulties in manufacturing. However, the major problem with the implantable agent dispensers of conventional design is that there is no assurance that the agent dispenser will not disassemble during use. Upon disassembly, the agent in the dispenser will be dispensed at a much greater rate than is desirable or safe; thus, a need exists for an improved, implantable fluid imbibing pump which remains completely assembled at all times while in use. The present invention fulfills this need by virtue of an improved closure for closing the ends of the membrane and bag to form the agent dispenser.